Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the prior art described above. Therefore, the invention provides a preparation method of polyhydroxyalkanoate particles, which can reduce the degradation of polyhydroxyalkanoate and is beneficial to secondary processing and subsequent use of polyhydroxyalkanoate.
In a first aspect, the present invention provides a polyhydroxyalkanoate particle.
Specifically, the polyhydroxyalkanoate particles comprise the following components: polyhydroxyalkanoates, anionic starches and thickeners.
Preferably, the anionic starch is starch with anionic groups obtained after chemical treatment. Further preferably, the anionic starch is selected from at least one of carboxymethyl starch, starch sulfate, starch succinate monoester, starch phosphate or starch acetate.
Preferably, the thickener is a cellulosic or polysaccharide. Further preferably, the thickener is selected from at least one of xanthan gum, pectin, agar, hydroxyethyl cellulose, hydroxypropyl methylcellulose, sodium hydroxypropyl methylcellulose or methylcellulose.
Preferably, the thickener comprises hydroxymethyl cellulose and/or sodium hydroxymethyl cellulose, which not only has a thickening effect, but also improves the finish of the PHA granule surface.
More preferably, the thickener comprises methylcellulose and sodium hydroxypropyl methylcellulose.
Preferably, the polyhydroxyalkanoate has a weight average molecular weight of 5-80 ten thousand Da. Such as 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80.
Preferably, the Polyhydroxyalkanoates (PHAs) include, but are not limited to, poly-beta-hydroxybutyrate (PHB), copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate (PHBV), copolyesters of 3-hydroxybutyrate with 3-hydroxyhexanoate (PHBHHx), and poly (3-hydroxybutyrate-co-4-hydroxybutyrate) (P34 HB).
Preferably, the mass ratio of the polyhydroxyalkanoate to the anionic starch is (2-20): 1; further preferably, the mass ratio of the polyhydroxyalkanoate to the anionic starch is (3-19): 1; more preferably, the mass ratio of the polyhydroxyalkanoate to the anionic starch is (5-15): 1.
Preferably, the mass ratio of the polyhydroxyalkanoate to the thickener is (5-35): 1; further preferably, the mass ratio of the polyhydroxyalkanoate to the thickener is (6.5-32): 1; more preferably, the mass ratio of the polyhydroxyalkanoate to the thickener is (10-25): 1.
In a second aspect, the present invention provides a method of preparing polyhydroxyalkanoate particles.
Specifically, the preparation method of the polyhydroxyalkanoate particles comprises the following steps:
mixing polyhydroxyalkanoate powder, anionic starch and thickener, and pressing at 5-40deg.C under 40-120kN to obtain polyhydroxyalkanoate granule.
PHA is a high molecular polymer with a melting point between 80 and 180 ℃ depending on the monomers polymerized. The pelletization using a twin screw extruder is to melt the PHA at the melting point of the PHA by heating, then extrude the PHA by shearing force of the twin screw, cool the extrusion, and cut to form PHA pellets. This approach can lead to degradation of the PHA, formation of monomeric compounds such as 3-hydroxybutyric acid and other oligomers, resulting in a decrease in PHA molecular weight and a consequent significant change in physical properties, which can adversely affect subsequent use.
The invention adds anionic starch and thickener into polyhydroxyalkanoate powder, and prepares PHA particles at normal temperature (5-40 ℃) by using a pressure granulation mode. The anionic starch can balance cations in the polyhydroxyalkanoate powder, reduce the rejection between polyhydroxyalkanoate powder, and is matched with a thickening agent, especially methylcellulose and sodium hydroxymethyl cellulose for use, so that the prepared polyhydroxyalkanoate particles have smooth particle surfaces, high smoothness, no powder falling, high particle forming degree and difficult loosening and particle breakage; and can effectively reduce the degradation of polyhydroxyalkanoate.
Preferably, the polyhydroxyalkanoate powder is obtained by passing through a 40 mesh screen.
Preferably, the polyhydroxyalkanoate powder has a moisture content of less than 4%; further preferably, the polyhydroxyalkanoate powder has a moisture content of less than 2%. The subsequent preparation of the polyhydroxyalkanoate particles is facilitated by controlling the moisture content.
Preferably, the pressing process is to press at 5-35 ℃ with a pressure of 40-100 kN; further preferably, the pressing is performed at 15-35 ℃ under a pressure of 60-90 kN.
Preferably, the pressing time is 5-90s; such as 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 60s, 65s, 70s, 75s, 80s, 85s, 90s.
Preferably, the weight of each of the polyhydroxyalkanoate particles is 0.1-1.0 gram; further preferably, the weight of each of the polyhydroxyalkanoate particles is 0.2-0.8 grams.
More specifically, a method for preparing polyhydroxyalkanoate particles comprises the following steps:
fully mixing polyhydroxyalkanoate powder, anionic starch and a thickener in a mixer, controlling the weight of single particles to be 0.2-0.8 g, and pressing for 5s-90s at a temperature of 5-40 ℃ under a pressure of 40-120kN to obtain polyhydroxyalkanoate particles.
Compared with the prior art, the invention has the following beneficial effects:
the components are selected, the anionic starch is matched with the thickener, and PHA particles are prepared at normal temperature (5-40 ℃) in a pressure granulation mode, so that the prepared PHA particles are smooth and bright in surface, high in particle forming degree and not easy to loose and break; and through the selection of components and the selection of granulation modes, the degradation of polyhydroxyalkanoate can be reduced, the molecular weight of polyhydroxyalkanoate in PHA particles is almost unchanged, and the secondary processing and subsequent use of polyhydroxyalkanoate are facilitated.
Detailed Description
In order to make the technical solutions of the present invention more apparent to those skilled in the art, the following examples will be presented. It should be noted that the following examples do not limit the scope of the invention.
The polyhydroxyalkanoate powder (PHA powder) used in the following examples and comparative examples is poly (3-hydroxybutyrate-co-4-hydroxybutyrate), and all materials, reagents or equipment are commercially available as they are or by known methods unless otherwise specified.
Example 1
The polyhydroxyalkanoate granule consists of the following components in parts by weight: 86 parts of polyhydroxyalkanoate, 8 parts of carboxymethyl starch, 2 parts of methylcellulose and 2 parts of sodium hydroxymethyl cellulose.
A method for preparing polyhydroxyalkanoate particles, comprising the steps of: weighing PHA powder with water content of 0.4% and weight average molecular weight of about 10 ten thousand Da (sieving with 40 mesh sieve), and adding carboxymethyl starch, methyl cellulose and sodium hydroxymethyl cellulose into a three-dimensional mixer, and mixing for 24 hr until mixing thoroughly; the PHA granules were then prepared by pressing at a temperature of 20℃for 10 seconds under a pressure of 70kN, with the individual granules weighing 0.3 g, using a die of 6mm by 4 mm.
The PHA particles were analyzed by GPC for weight average molecular weight, which was still about 10 kiloDa with little change. And PHA particles have smooth surfaces and do not fall off powder.
Similar effects can be obtained by preparing polyhydroxyalkanoate granules from other PHA powders, such as PHB, PHBV and PHBHHx.
Example 2
The polyhydroxyalkanoate granule consists of the following components in parts by weight: 90 parts of polyhydroxyalkanoate, 5 parts of carboxymethyl starch, 2 parts of methylcellulose and 1 part of sodium hydroxymethyl cellulose.
A method for preparing polyhydroxyalkanoate particles, comprising the steps of: weighing PHA powder with water content of 0.4% and weight average molecular weight of about 10 ten thousand Da (sieving with 40 mesh sieve), and adding carboxymethyl starch, methyl cellulose and sodium hydroxymethyl cellulose into a three-dimensional mixer, and mixing for 24 hr until mixing thoroughly; the PHA granules were then prepared by pressing at a temperature of 20℃for 10 seconds under a pressure of 70kN, with the individual granules weighing 0.3 g, using a die of 6mm by 4 mm.
The PHA particles were analyzed by GPC for weight average molecular weight, which was about 9.8 Da. PHA particles have smooth surfaces and do not fall off powder.
Example 3
The polyhydroxyalkanoate granule consists of the following components in parts by weight: 110 parts of polyhydroxyalkanoate, 5 parts of carboxymethyl starch, 2 parts of methylcellulose and 1 part of sodium hydroxymethyl cellulose.
A method for preparing polyhydroxyalkanoate particles, comprising the steps of: weighing PHA powder with water content of 0.4% and weight average molecular weight of about 10 ten thousand Da (sieving with 40 mesh sieve), and adding carboxymethyl starch, methyl cellulose and sodium hydroxymethyl cellulose into a three-dimensional mixer, and mixing for 24 hr until mixing thoroughly; the PHA granules were then prepared by pressing at a temperature of 20℃for 10 seconds under a pressure of 70kN, with the individual granules weighing 0.3 g, using a die of 6mm by 4 mm.
The PHA particles were analyzed by GPC for weight average molecular weight, which was about 9.7 kiloDa. PHA particles have smooth surfaces and do not fall off powder.
Example 4
The polyhydroxyalkanoate granule consists of the following components in parts by weight: 86 parts of polyhydroxyalkanoate, 8 parts of carboxymethyl starch, 2 parts of methylcellulose and 2 parts of sodium hydroxymethyl cellulose.
A method for preparing polyhydroxyalkanoate particles, comprising the steps of: weighing PHA powder with water content of 0.4% and weight average molecular weight of about 10 ten thousand Da (sieving with 40 mesh sieve), and adding carboxymethyl starch, methyl cellulose and sodium hydroxymethyl cellulose into a three-dimensional mixer, and mixing for 24 hr until mixing thoroughly; the PHA granules were then prepared by pressing at a temperature of 40℃for 10 seconds under a pressure of 70kN, with the individual granules weighing 0.3 g, using a die of 6mm by 4 mm.
The PHA particles were analyzed by GPC for weight average molecular weight, which was about 9.5 Da. PHA particles have smooth surfaces and do not fall off powder.
Example 5
The polyhydroxyalkanoate granule consists of the following components in parts by weight: 86 parts of polyhydroxyalkanoate, 8 parts of carboxymethyl starch, 2 parts of methylcellulose and 2 parts of sodium hydroxymethyl cellulose.
A method for preparing polyhydroxyalkanoate particles, comprising the steps of: weighing PHA powder with water content of 0.4% and weight average molecular weight of about 10 ten thousand Da (sieving with 40 mesh sieve), and adding carboxymethyl starch, methyl cellulose and sodium hydroxymethyl cellulose into a three-dimensional mixer, and mixing for 24 hr until mixing thoroughly; the PHA granules were then prepared by pressing at a pressure of 110kN for 10 seconds with a die of 6mm by 4mm, with the individual granules weighing 0.3 g, at a temperature of 20 ℃.
The PHA particles were analyzed by GPC for weight average molecular weight, which was about 9.8 Da. PHA particles have smooth surfaces and do not fall off powder, but in the pressing process, the granularity of the materials is poor, and cracking particles can appear.
Example 6
The polyhydroxyalkanoate granule consists of the following components in parts by weight: 86 parts of polyhydroxyalkanoate, 8 parts of starch sulfate, 2 parts of hydroxyethyl cellulose and 2 parts of sodium hydroxymethyl cellulose.
A method for preparing polyhydroxyalkanoate particles, comprising the steps of: weighing PHA powder with water content of 0.4% and weight average molecular weight of about 37 ten thousand Da (sieving with 40 mesh sieve), adding starch sulfate, hydroxyethyl cellulose and sodium hydroxymethyl cellulose into a three-dimensional mixer, and mixing for 24 hr until mixing thoroughly; the PHA granules were then prepared by pressing at 80kN for 12s using a die of 6mm by 4mm gauge, with the individual granules weighing 0.3 g, at a temperature of 20 ℃.
The PHA particles were analyzed by GPC for weight average molecular weight, which was still about 37 kiloDa with little change. The surface of the particles is smooth, and powder is not dropped; but loosening of the particles occurs.
Example 7
The polyhydroxyalkanoate granule consists of the following components in parts by weight: 85 parts of polyhydroxyalkanoate, 8 parts of starch succinate monoester, 2 parts of methylcellulose, 2 parts of sodium hydroxymethyl cellulose and 1 part of hydroxypropyl methylcellulose.
A method for preparing polyhydroxyalkanoate particles, comprising the steps of: weighing PHA powder with water content of 0.4% and weight average molecular weight of about 52 Da (sieving with 40 mesh sieve), and adding starch succinic acid monoester, methylcellulose, sodium hydroxymethyl cellulose and hydroxypropyl methylcellulose into a three-dimensional mixer, and mixing for 24 hr until mixing thoroughly; the PHA granules were then prepared by pressing at a temperature of 15℃for 30 seconds under a pressure of 50kN, with the weight of the individual granules controlled to be 0.3 g, using a die having a gauge of 6mm by 4 mm.
The PHA particles were analyzed by GPC for weight average molecular weight, which was still about 52 kiloDa, with little change; and the surface of the particles is smooth, and the powder is not dropped.
Example 8
The polyhydroxyalkanoate granule consists of the following components in parts by weight: 86 parts of polyhydroxyalkanoate, 8 parts of carboxymethyl starch, 2 parts of methylcellulose and 2 parts of xanthan gum.
A method for preparing polyhydroxyalkanoate particles, comprising the steps of: weighing PHA powder with water content of 0.4% and weight average molecular weight of about 10 ten thousand Da (sieving with 40 mesh sieve), and adding carboxymethyl starch, methylcellulose and xanthan gum into a three-dimensional mixer, and mixing for 24 hr until mixing thoroughly; the PHA granules were then prepared by pressing at a temperature of 20℃for 10 seconds under a pressure of 70kN, with the individual granules weighing 0.3 g, using a die of 6mm by 4 mm.
The PHA particles were analyzed by GPC for weight average molecular weight, which was still about 10 kiloDa with little change. However, the PHA particles were not as smooth as the PHA particles prepared in example 1, and the PHA particles had a matte surface and were prone to dusting.
Comparative example 1
The polyhydroxyalkanoate granule consists of the following components in parts by weight: 86 parts of polyhydroxyalkanoate, 8 parts of carboxymethyl starch, 2 parts of methylcellulose and 2 parts of sodium hydroxymethyl cellulose.
A method for preparing polyhydroxyalkanoate particles, comprising the steps of:
weighing PHA powder with water content of 0.4% and weight average molecular weight of about 10 ten thousand (sieving with 40 mesh sieve), and carboxymethyl starch, methyl cellulose and sodium hydroxymethyl cellulose, adding into a three-dimensional mixer, and mixing for 24 hr to obtain mixture;
preheating a double-screw extruder: and (5) turning on a power supply, setting the temperature of each temperature zone of the extruder to be 135 ℃ and starting to heat. And starting a cooling circulating water refrigerating system, and setting the water temperature to 15 ℃. After the temperature reached 135 ℃, the constant temperature was continued for 30 minutes. Then, the cooling water circulation is started, and the mixture is put into a double-screw extruder. After the mixture reaches a molten state through different temperature areas, extruding the mixture in a linear shape through an outlet; after the extruded linear PHA is cooled by cooling water, the linear PHA is pulled to a granulator by a tractor, and the granulator cuts the linear PHA into granular PHA to prepare PHA particles.
The weight average molecular weight of the PHA particles was analyzed by GPC, and the weight average molecular weight of the PHA particles prepared in comparative example 1 was reduced to about 4 ten thousand Da, which was reduced by more than half as compared with the weight average molecular weight of the raw PHA powder.
Comparative example 2
Comparative example 2 differs from example 1 in that 4 parts of methylcellulose and 4 parts of sodium hydroxymethylcellulose are used instead of carboxymethyl starch, the remainder of the components and the preparation process being the same as in example 1.
The PHA particles were analyzed by GPC for weight average molecular weight, which was still about 10 kiloDa with little change. But PHA particles have poor formability and are easy to loosen, and the phenomena of block falling and particle breakage occur in the placing process.
Comparative example 3
Comparative example 3 was different from example 1 in that PHA granules were produced by pressing at a pressure of 35kN for 30 seconds under a temperature condition of 20℃and the components of PHA granules and the remaining production method were the same as in example 1.
The PHA particles were analyzed by GPC for weight average molecular weight, which was still about 10 kiloDa with little change. But PHA particles have poor formability and are easy to loosen, and the phenomena of block falling and particle breakage occur in the placing process.